Various different forms of structures relative to which a vehicle body may be mounted heretofore have been provided and at least some of these structures include datum line establishing means from which various vehicle body dimensions may be taken in order to determine whether or not a vehicle body or frame needs to be straightened. However, upper vehicle body component locations are difficult to measure relative to a datum line and the conventional method of making such measurements is time consuming and requires repeated reference to various different dimension tables. Accordingly, a need exists for structure by which the positioning of one vehicle frame or body component on one side of a longitudinal vertical center plane passing through an associated vehicle may be checked relative to the positioning of a corresponding component on the other side of the center plane. Further, an additional need exists to enable such positional determinations to be made quickly, easily and accurately without the need for continued reference to a manufacturers frame and body dimension table.